Mitosis POGIL Key

Mitosis How do living things grow and repair themselves? Why? Living things must grow and develop. At times they suffer injuries or damage, or cells simply wear out. New cells must be formed for the organism to survive. What process must occur to make a new, properly functioning cell? Model 1- Mitosis as Part of the Cell Cycle Prophase Metaphase Anaphase Telophase Mitosis (Nuclear Division) Cytokinesis (Cytoplasmic Division) * Centrinle Replicated chromosome (2 sister chromatids) Noclear Spindle fibers 1. Refer to Model 1. List the four phases in the mitosis process. Prophase, Metaphase, Anaphase, Telophase 2. Where is mitosis in the cell cycle? Before Cytokinesis Gap2/and after interphase. 3. What three phases of the cell cycle are considered interphase? G G2 S 4. Refer to the cell cycle shown. 4. How many cells are present at the beginning of mitosis? 6. How many cells are present at the end of mitosis? 2 5. Refer to the chromosomes in the cells in Model 1. unreplicated a. Draw a single chromosome as it appears in Model 1. & Draw a replicated chromosome as it appears in Model 1. X How many chromatids are in each replicated chromosome? 2 6. How many replicated chromosomes are in the original cell shown in Model 1 during prophase? Hint: When counting chromosomes, count "1" for a pair of sister chromatids. 4 7. How many single chromosomes are in each of the new cells in telophase? 4 8. As a group, write a grammatically correct sentence that explains what a chromosome is and why it is important. A single molecule of DNA wrapped around histone proteins. It contains many instructions for the cell. 9. Refer to the cells in telophase in Model 1. 4. Use a complete sentence to describe what the new cells in telophase might contain if replica-tion of chromosomes did not occur before cytokinesis. They might only contain 2 chromosomes. 6. If the situation in part a occurred, would the new cells be viable? Explain. STOP No. The chromosome number must be maintained because an organism cannot survive with only half of its Chromosomes. 10. The S phase stands for synthesis, which means to make or build something more complex out of simpler parts. Scientists know that during the S phase DNA is being made in the nucleus of the cell. Why do you think the cell needs to make more DNA at this time in the cell cycle? To make sure there are 2 complete copies of the DNA→ one for each daughter cell.. 11. Refer to Model 1. The chromosomes that are shaped like "X" (made of two sister chromatids) have double the amount of DNA than the chromosomes that are shaped like "1." During what phase of the cell cycle do you think the chromosomes are replicated (copied)? Sphase 12. Refer to Model 1. 4. In which phase of mitosis do you see the spindle fibers forming? Prophase b. At wluat phase of mitosis do the replicated chromosomes (sister chromatids) separate? Anapnáse c. In which phase do you see that the spindle fibers have disappeared? Telophase d. Look at meraphase and anaphase. Suggest the purpose of the spindle fibers during mitosis. To pull sister chromatids apart & move the individual Chromosomes to opposite sides of the cell. 13. Refer to Model 1. 4. Describe what happens to the nuclear membrane after prophase. It disappears 6. Explain why it is necessary that the nuclear membrane disintegrates during mitosis. The chromosomes must be pulled to opposite ends of the cell. c. At what point during mitosis has the nuclear membrane reformed? Telophase 14. What is actually dividing during cytokinesis? Cytoplasm 15. Cellular division has two parts-mitosis is the division of the nucleus and cytokinesis is the division of the cell into two new cells. Explain why mitosis has to come before cytokinesis in the cell cycle. The chromosomes needed to be pulled to opposite ends of the cell before it split, so the chromosomes could be divided 16. During cytokinesis the chromosomes unwind and become a pile of very long, thin, thread-like DNA and the cell goes back to looking "normal" until mitosis begins again. Brainstorm with your group ideas why the DNA must coil up into chromosome structures before it divides. egrally between the 2 daughter cetts. Keep chromosomes organized & from breaking 17. Fill in the table below where each of the phases of nuclear and cell division is listed in the left hand column and write a description of what is happening during that phase in the right hand column. Phase of Cellular Division Description of what is occurring in the cell during this phase. P Spindle forms, nuclear envelope dissolves, chromosomes condense M Chromosomes line up along cell equator A Spindle pulls sister chrornatids to opposite ends of cell. T 2 new nuclei reform, spindle disappears, DNA Chromosomes loosen C Cytoplasm splits. 18. In some cells, mitosis occurs without cytokinesis. What would the resulting cell look like? A cell with 2 nuclei and twice the number of chromosomes 19. Explain the importance of mitosis of cells in a skinned knee and during the growth of a plant. Skinned knee- cell division replaces missing/damaged cells. Plant growth-necessary for plant to grow taller & wider and for roots to grow deeper. 20. With your group, consider the effect on a cell if the sister chromatids did not line up correctly during metaphase. For example, if some lined up side by side instead of single file along the middle, how might this affect the resulting cells? The resulting cells might get too many or too few chromosomes. STOP